1. Field of Invention
The present disclosure relates to a rotor core for a BLDC motor.
2. Background
This section provides background information related to the present disclosure which is not necessarily prior art.
In general, a rotor of a BLDC (Brushless direct current) motor is formed by press-fitting a shaft into a rotor core formed by being stacked with thin rotor core members. At this time, the rotor core member is arranged with magnet insertion holes, each at a predetermined gap, for inserting a magnet at a position near to a periphery.
Each shape of the magnet insertion hole is so arranged as to correspond to that of the magnet that is to be inserted, and each magnet generally takes an approximately trapezoidal shape to form pockets at both sides of the magnet insertion hole.
However, in a case the magnet insertion hole is formed with a shape a bit different from that of the magnet, the magnet may move or rotate inside the magnet insertion hole to generate a horizontal position scattering inside the rotor core, because of decreased adhesive force of an adhesive in long term use even if the magnet is secured by the adhesive.
In a case the horizontal position scattering by the position change is generated, a cogging torque becomes unstable due to inconsistent maintenance of magnetic force in the rotor to disadvantageously deteriorate a control characteristic of the rotor.
Furthermore, although the magnet is restricted in rotation by the centrifugal force generated by rotation of the rotor core, the magnet may be axially disengaged during rotation of the rotor core, because there is no separate support structure to an axial direction of the shaft rotatably supporting the rotor core.
In a case the magnet is rotated to the axial direction of the shaft, the magnetic force generated by the rotor core cannot be constantly maintained to deteriorate an operability of the motor and to make it difficult to perform an accurate control.
It is, therefore, desirable to overcome the above problems and others by providing an improved rotor core of a motor.